Currently, fiber distributed data interface (FDDI) concentrator systems are designed and built with discrete elastic buffer and layer management (ELM) circuits, inadequate discreet multiplexed interconnection circuitry, and other discrete components. This type of design causes a number of problems. Not only are discrete ELM parts used, but the switching matrix, the logic to control the switching matrix, and all of the buses that couple these systems are implemented discretely. The board size of current FDDI concentrators is very large due to the use of discrete parts. The large board size and number of components make the concentrator systems unduly costly. Furthermore, the inadequate discreet multiplexed interconnection circuitry does not allow for exhaustive, flexible, FDDI specification compatible interconnections in all possible FDDI scenarios.
Specifically, the switching matrixes in current concentrators are made up of multiplexers. These multiplexers are expensive to implement discretely, and their flexibility is limited. In order to meet all of the requirements of Station Management (SMT) software, a very large number of multiplexers would be necessary. Discrete systems normally compromise and have a limited number of multiplexers that give a limited amount of interconnection flexibility. These systems are not fully compliant with the mandates of SMT.
The muxing structures that normally make up the switching matrix are very difficult to control. The control circuitry that is also implemented discretely is therefore complex, and the software that controls them is also difficult. Having to deal with these types of problems increases the design time for a concentrator. Not only is the hardware design more time consuming, but complex control software also increases design cycle time.